1. Technical Field of the Invention
The present invention relates to a wavelength conversion device.
2. Related Art
Non-linear optical crystals such as a lithium niobate single crystal and a lithium tantalate single crystal have a high secondary non-linear optical constant; and forming a periodic polarization inversion configuration in these crystals produces a Quasi-Phase-Matched (QPM) Secondary-Harmonic-Generation (SHG) device. And forming a waveguide in this periodic polarization inversion configuration will produce a high efficient SHG device, which leads to a wide variety of applications for optical communication, medical, photochemical, and various optical measurement fields.
The light modulation device disclosed in the WO 03/042749 has a configuration such that the surface of a supporting substrate is made flat, the thickness of a ferroelectric thin plate is made constant, and the flat surface of the supporting substrate is bonded to the ferroelectric thin plate.
Japanese Patent Publication No. 2003-156723A provides a ridge optical waveguide on a ferroelectric single crystal thin plate, and forms a periodic polarization inversion configuration in the ridge optical waveguide to make a Secondary-Harmonic-Generation device. And a supporting substrate is bonded below the ferroelectric single crystal thin plate, and a recession is made on the supporting substrate in a manner that the recession is located right below the ridge optical waveguide. The supporting substrate and the back of the ferroelectric thin plate are bonded by a resin adhesive or a conductive adhesive.